my @IDnumber=();  #Initialize this...
while (my @row1 = $sth ->fetchrow_array){
    push @IDnumber,[@row1]; # save the row as an anon-array
    print "@row1\n";  #All the elements were printed out by this state
+ment.
        @IDnumber=@row1;
}
print "@row1\n";  #this is going to be empty! 
# snip! print  "@IDnumber\n";
foreach my $row(@IDnumber){
    printf "%s\n",join(",",@$row);
}